The principal goal of this work is to study the biological, biochemical, and biophysical characteristics of the replication of Respiratory Syncytial (RS) virus. A purification scheme which separates the RS virus particle from a contaminating pseudo-virus particle containing DNA has been developed. The RNA of the virion and its polypeptide composition will be studied. Also the characteristics of the virion RNA-dependent RNA polymerase are to be investigated. Cells infected with RS virus are being studied to elucidate the kinetics of virus-specific RNA synthesis, both virion RNA and messenger RNA. Similarly, we plan to examine the kinetics of virus protein synthesis in vivo, that is, in the infected cell. The effects of various DNA and RNA inhibitors on virus replication are also being studied.